Benzimidazole topoisomerase poisons

ABSTRACT

The invention provides a topoisomerase poison of formula I:                    
     wherein R 1 -R 8  have any of the meanings defined in the specification, or a pharmaceutically acceptable salt thereof, as well as pharmaceutical compositions comprising a compound of formula I or a salt thereof, intermediates useful for preparing a compound of formula I, and therapeutic methods comprising administering a compound of formula I or a salt thereof.

This application is a Continuation of U.S. patent application Ser. No.09/484,402, filed on Jan. 14, 2000 now U.S. Pat. No. 6,221,892, which isa Division of U.S. patent application Ser. No. 09/023,147, filed on Feb.12, 1998, now issued U.S. Pat. No. 6,063,801, issued on May 16, 2000.

GOVERNMENT FUNDING

The invention described herein was made with government support undergrant CA-39662 awarded by the National Cancer Institute. The UnitedStates Government has certain rights in the invention.

BACKGROUND OF THE INVENTION

DNA-topoisomerases are enzymes present in the nuclei of cells where theycatalyze the breaking and rejoining of DNA strands, controlling thetopological state of DNA. Recent studies also suggest thattopoisomerases are involved in regulating template supercoiling duringRNA transcription. There are two major classes of mammaliantopoisomerases. DNA-topoisomerase-I catalyzes changes in the topologicalstate of duplex DNA by performing transient single-strand breakage-unioncycles. In contrast, mammalian topoisomerase II alters the topology ofDNA by causing a transient enzyme bridged double-strand break, followedby strand passing and resealing. Mammalian topoisomerase II has beenfurther classified as Type II α and Type II β. The antitumor activityassociated with agents which are topoisomerase poisons is associatedwith their ability to stabilize the enzyme-DNA cleavable complex. Thisdrug-induced stabilization of the enzyme-DNA cleavable complexeffectively converts the enzyme into a cellular poison.

Several antitumor agents in clinical use have potent activity asmammalian topoisomerase II poisons. These include adriamycin,actinomycin D, daunomycin, VP-16, and VM-26 (teniposide orepipodophyllotoxin).

In contrast to the number of clinical and experimental drugs which actas topoisomerase II poisons, there are currently only a limited numberof agents which have been identified as topoisomerase I poisons.Camptothecin and its structurally-related analogs are among the mostextensively studied topoisomerase I poisons. Recently, bi- andterbenzimidazoles (Chen et al., Cancer Res. 1993, 53, 1332-1335; Sun etal., J. Med. Chem. 1995, 38, 3638-3644; Kim et al., J Med. Chem. 1996,39, 992-998), certain benzo[c]phenanthridine and protoberberinealkaloids and their synthetic analogs (Makhey et al., Med. Chem. Res.1995, 5, 1-12; Janin et al., J. Med. Chem 1975, 18, 708-713; Makhey etal., Bioorg. & Med. Chem. 1996, 4, 781-791), as well as the fungalmetabolites, bulgarein (Fujii et al., J. Biol. Chem. 1993, 268,13160-13165) and saintopin (Yamashita et al., Biochemistry 1991, 30,5838-5845) and indolocarbazoles (Yamashita et al., Biochemistry 1992,31, 12069-12075) have been identified as topoisomerase I poisons.

Presently, a need exists for novel anti-cancer agents, for anti-canceragents that exhibit improved activity, and for anti-cancer agents thatexhibit fewer side-effects or improved selectivity compared to existingagents.

SUMMARY OF THE INVENTION

The present invention provides compounds that exhibit inhibitoryactivity against topoisomerase I, and compounds that are effectivecytotoxic agents against cancer cells, including drug-resistant cancercells. Accordingly there is provided a compound of the invention whichis a compound of formula I:

wherein

R₁ and R₂ are each independently hydrogen, (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆) alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio,(C₁-C₆)alkanoyloxy, aryl, heteroaryl, aryl(C₁-C₆)alkyl, orheteroaryl(C₁-C₆)alkyl; or R₁ and R₂ taken together are methylenedioxy;or R₁ and R₂ taken together are benzo;

R₃, R₄, and R₅ are each independently selected from the group consistingof hydrogen, (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₂-C₆)alkanoyloxy, aryl, heteroaryl,aryl(C₁-C₆)alkyl, and heteroaryl(C₁-C₆)alkyl;

R₆ and R₇ are each independently hydrogen, (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)akyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or(C₁-C₆)alkanoyloxy;

R₈ is hydroxy, halo, nitro, cyano, mercapto, carboxy, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, —NR_(a)R_(b), halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, (C₁-C₆)alkanoyloxy, aryloxy, or heteroaryloxy; or R₈is (C₁-C₆)alkyl substituted by 1, 2, or 3 substituents independentlyselected from the group consisting of hydroxy, nitro, cyano, mercapto,carboxy, (C₁-C₆)alkoxy, (C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, —NR_(a)R_(b),trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, (C₁-C₆)alkanoyloxy, aryloxy, and heteroaryloxy; and

each of R_(a) and R_(b) is independently hydrogen, (C₁-C₆)alkyl,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyi, aryl, heteroaryl,aryl(C₁-C₆)alkyl, heteroaryl(C₁-C₆)alkyl, arylcarbonyl, orheteroarylcarbonyl; or R_(a) and R_(b) together with the nitrogen towhich they are attached are pyrrolidino, piperidino, or morpholino.

wherein any aryl, heteroaryl, or benzo of R₁-R₅, R₈, R_(a), and R_(b)may optionally be substituted by 1, 2, or 3 substituents independentlyselected from the group consisting of (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and(C₁-C₆)alkanoyloxy;

or a pharmaceutically acceptable salt thereof.

The invention also provides a compound of the invention which is acompound of formula I:

wherein

R₁ and R₂ are each independently (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio,(C₁-C₆)alkanoyloxy, aryl, heteroaryl, aryl(C₁-C₆)alkyl, orheteroaryl(C₁-C₆)alkyl; or R₁ and R₂ taken together are methylenedioxy;

R₃, R₄, and R₅ are each independently selected from the group consistingof hydrogen, (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₂-C₆)alkanoyloxy, aryl, heteroaryl,aryl(C₁-C₆)alkyl, and heteroaryl(C₁-C₆)alkyl;

R₆ and R₇ are each independently hydrogen, (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or(C₁-C₆)alkanoyloxy; and

R₈ is hydrogen, (C₁-C₆)alkyl, aryl, or heteroaryl;

wherein any aryl or heteroaryl of R₁-R₅ and R₈ may optionally besubstituted by 1, 2, or 3 substituents independently selected from thegroup consisting of (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and(C₁-C₆)alkanoyloxy;

or a pharmaceutically acceptable salt thereof.

The invention also provides a pharmaceutical composition comprising acompound of formula I, or a pharmaceutically acceptable salt thereof, incombination with a pharmaceutically acceptable carrier.

The invention also provides a therapeutic method comprising inhibitingcancer cells by administering to a mammal (e.g. a human) in need of suchtherapy, an amount of a compound of formula I, or a pharmaceuticallyacceptable salt thereof, effective to inhibit said cancer cells.

The invention also provides a method comprising inhibiting cancer cellsby contacting said cancer cells in vitro or in vivo with an amount of acompound of formula I, or a pharmaceutically acceptable salt thereof,effective to inhibit said cancer cells, i.e. to inhibit their activity,such as their ability to divide, migrate, or proliferate.

The invention also provides a compound of formula I for use in medicaltherapy (preferably for use in treating cancer, e.g. solid tumors; orfor use as an antifungal agent), as well as the use of a compound offormula I for the manufacture of a medicament useful for the treatmentof cancer, e.g. solid tumors, and the use of a compound of formula I forthe manufacture of a medicament useful for the treatment of fungalinfeaction.

The invention also provides processes and novel intermediates disclosedherein which are useful for preparing compounds of the invention. Someof the compounds of formula I are useful to prepare other compounds offormula I.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the structure of representative compounds of the inventionand other compounds (1, 6, 9, 14, 17, and 19).

FIG. 2 shows biological data for representative compounds of formula I.

DETAILED DESCRIPTION

The following definitions are used, unless otherwise described: halo isfluoro, chloro, bromo, or iodo. Alkyl, alkoxy, etc. denote both straightand branched groups; but reference to an individual radical such as“propyl” embraces only the straight chain radical, a branched chainisomer such as “isopropyl” being specifically referred to. Aryl denotesa phenyl radical or an ortho-fused bicyclic carbocyclic radical havingabout nine to ten ring atoms in which at least one ring is aromatic.Heteroaryl encompasses a radical attached via a ring carbon of amonocyclic aromatic ring containing five or six ring atoms consisting ofcarbon and one to four heteroatoms each selected from the groupconsisting of non-peroxide oxygen, sulfur, and N(Y) wherein Y is absentor is H, O, (C₁-C₄)alkyl, phenyl or benzyl, as well as a radical of anortho-fused bicyclic heterocycle of about eight to ten ring atomsderived therefrom, particularly a benzo-derivative or one derived byfusing a propylene, trimethylene, or tetramethylene diradical thereto.

It will be appreciated by those skilled in the art that compounds of theinvention having a chiral center may exist in and be isolated inoptically active and racemic forms. Some compounds may exhibitpolymorphism. It is to be understood that the present inventionencompasses any racemic, optically-active, polymorphic, orstereoisomeric form, or mixtures thereof, of a compound of theinvention, which possess the useful properties described herein, itbeing well known in the art how to prepare optically active forms (forexample, by resolution of the racemic form by recrystallizationtechniques, by synthesis from optically-active starting materials, bychiral synthesis, or by chromatographic separation using a chiralstationary phase) and how to determine topoisomerase poisoning activityor cytotoxic activity using the standard tests described herein, orusing other similar tests which are well known in the art.

Specific and preferred values listed below for radicals, substituents,and ranges, are for illustration only; they do not exclude other definedvalues or other values within defined ranges for the radicals andsubstituents Specifically, (C₁-C₆)alkyl can be methyl, ethyl, propyl,isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, or hexyl;(C₃-C₆)cycloalkyl can be cyclopropyl, cyclobutyl, cyclopentyl, orcyclohexyl; (C₃-C₆)cycloalkyl(C₁-C₆)alkyl can be cyclopropylmethyl,cyclobutylmethyl, cyclopentylmethyl, cyclohexylmethyl,2-cyclopropylethyl, 2-cyclobutylethyl, 2-cyclopentylethyl, or2-cyclohexylethyl; (C₁-C₆)alkoxy can be methoxy, ethoxy, propoxy,isopropoxy, butoxy, iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, orhexyloxy; (C₁-C₆)alkanoyl can be acetyl, propanoyl or butanoyl;halo(C₁-C₆)alkyl can be iodomethyl, bromomethyl, chloromethyl,fluoromethyl, trifluoromethyl, trichloromethyl, 2-chloroethyl,2-fluoroethyl, 2,2,2-trifluoroethyl, or pentafluoroethyl;hydroxy(C₁-C₆)alkyl can be hydroxymethyl, 1-hydroxyethyl,2-hydroxyethyl, 1-hydroxypropyl, 2-hydroxypropyl, 3-hydroxypropyl,1-hydroxybutyl, 4-hydroxybutyl, 1-hydroxypentyl, 5-hydroxypentyl,1-hydroxyhexyl, or 6-hydroxyhexyl; (C₁-C₆)alkoxycarbonyl can bemethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl,butoxycarbonyl, pentoxycarbonyl, or hexyloxycarbonyl; (C₁-C₆)alkylthiocan be methylthio, ethylthio, propylthio, isopropylthio, butylthio,isobutylthio, pentylthio, or hexylthio; (C₁-C₆)alkanoyloxy can beformyloxy, acetoxy, propanoyloxy, butanoyloxy, isobutanoyloxy,pentanoyloxy, or hexanoyloxy; aryl can be phenyl, indenyl, or naphthyl;and heteroaryl can be furyl, imidazolyl, triazolyl, triazinyl, oxazoyl,isoxazoyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl,tetrazolyl, pyridyl, (or its N-oxide), thienyl, pyrimidinyl (or itsN-oxide), indolyl, isoquinolyl (or its N-oxide) or quinolyl (or itsN-oxide).

A specific value for R₁ is hydrogen. Another specific value for R₁ ishalo (e.g. bromo).

A specific value for R₂ is phenyl, optionally substituted by 1, 2, or 3substituents independently selected from the group consisting of(C₁-C₆)alkyl, (C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, halo(C₁-C₆)alkyl, trifluoromethoxy, (C₁-C6)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and (C₁-C₆)alkanoyloxy. Anotherspecific value for R₂ is phenyl.

A specific value for each of R₃, R₄, and R₅ is hydrogen.

A specific value for R₆ or R₇ is (C₁-C₆)alkoxy, hydroxy, halo, nitro,cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy. Another specific value for eachof R₆ and R₇ is hydrogen.

A specific value for R₈ is hydroxy, halo, nitro, cyano, mercapto,carboxy, (C₁-C₆)alkoxy, —NR_(a)R_(b), halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy. Another specific value for R₈is (C₁-C₆)alkyl substituted by 1, 2, or 3 substituents independentlyselected from the group consisting of hydroxy, nitro, cyano, mercapto,carboxy, (C₁-C₆)alkoxy, —NR_(a)R_(b), trifluoromethoxy, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyL (C₁-C₆)alkylthio, and (C₁-C₆)alkanoyloxy. Anotherspecific value for R₈ is (C₁-C₆)alkyl substituted by hydroxy, nitro,cyano, mercapto, carboxy, (C₁-C₆)alkoxy, —NR_(a)R_(b), trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or(C₁-C₆)alkanoyloxy.

A preferred value for R₁ is hydrogen; for R₂ is phenyl; and for R₈ ishalo or trifluoromethyl. A more preferred value for R₈ istrifluoromethyl.

A preferred group of compounds of formula I wherein R₁ and R₂ are eachhalo (e.g. bromo).

Processes for preparing compounds of formula I are illustrated by thefollowing procedures in which the meanings of the generic radicals areas given above unless otherwise qualified.

A compound of formula I wherein R₈ is hydroxy can be prepared bytreating an intermediate of formula II:

with urea, for example, using conditions similar to those described inExample 1.

A compound of formula I wherein R₈ is mercapto can be prepared bytreating an intermediate of formula II with ethylxanthic acid potassiumsalt, for example, using conditions similar to those described inExample 2.

A compound of formula I wherein R₈ is amino can be prepared by treatingan intermediate of formula II with cyanogen bromide, for example, usingconditions similar to those described in Example 3.

Compounds of formula I can generically be prepared by reacting anintermediate diamine of formula III with an intermediate aldehyde offormula IV.

The reaction can conveniently be carried out under conditions similar tothose described in the Examples (e.g., Example 4).

Compounds of formula I can also generally be prepared by reacting anintermediate diamine of formula V with an aldehyde of formula VI.

The reaction can conveniently be performed under conditions similar tothose described in the Examples (e.g. Example 12).

Compounds of formula I comprising a hydroxy group can be prepared from acorresponding compound of formula I comprising a methoxy group bytreatment with boron tribromide, for example using conditions similar tothose described in Example 7.

Compounds of formula I comprising a amino group can be prepared from acorresponding compound of formula I comprising a acetamido group byhydrolysis using conditions similar to those described in Example 8.

Intermediates of formula II, III, IV, V, and VI wherein R₁-R₈ have anyof the values, specific values, or preferred values defined herein forthe corresponding radicals in a compound of formula I, are particularlyuseful for preparing compounds of formula I.

In cases where compounds are sufficiently basic or acidic to form stablenontoxic acid or base salts, administration of the compounds as saltsmay be appropriate. Examples of pharmaceutically acceptable salts areorganic acid addition salts formed with acids which form a physiologicalacceptable anion, for example, tosylate, methanesulfonate, acetate,citrate, malonate, tartarate, succinate, benzoate, ascorbate,α-ketoglutarate, and α-glycerophosphate. Suitable inorganic salts mayalso be formed, including hydrochloride, sulfate, nitrate, bicarbonate,and carbonate salts.

Pharmaceutically acceptable salts may be obtained using standardprocedures well known in the art, for example by reacting a sufficientlybasic compound such as an amine with a suitable acid affording aphysiologically acceptable anion. Alkali metal (for example, sodium,potassium or lithium) or alkaline earth metal (for example, calcium)salts of carboxylic acids can also be made.

The compounds of formula I can be formulated as pharmaceuticalcompositions and administered to a mammalian host, such as a humanpatient in a variety of forms adapted to the chosen route ofadministration, i.e., orally or parenterally, by intravenous,intramuscular, topical or subcutaneous routes.

Thus, the present compounds may be systemically administered, e.g.,orally, in combination with a pharmaceutically acceptable vehicle suchas an inert diluent or an assimilable edible carrier. They may beenclosed in hard or soft shell gelatin capsules, may be compressed intotablets, or may be incorporated directly with the food of the patient'sdiet. For oral therapeutic administration, the active compound may becombined with one or more excipients and used in the form of ingestibletablets, buccal tablets, troches, capsules, elixirs, suspensions,syrups, wafers, and the like. Such compositions and preparations shouldcontain at least 0.1% of active compound. The percentage of thecompositions and preparations may, of course, be varied and mayconveniently be between about 2 to about 60% of the weight of a givenunit dosage form. The amount of active compound in such therapeuticallyuseful compositions is such that an effective dosage level will beobtained.

The tablets, troches, pills, capsules, and the like may also contain thefollowing: binders such as gum tragacanth, acacia, corn starch orgelatin; excipients such as dicalcium phosphate; a disintegrating agentsuch as corn starch, potato starch, alginic acid and the like; alubricant such as magnesium stearate; and a sweetening agent such assucrose, fructose, lactose or aspartame or a flavoring agent such aspeppermint, oil of wintergreen, or cherry flavoring may be added. Whenthe unit dosage form is a capsule, it may contain, in addition tomaterials of the above type, a liquid carrier, such as a vegetable oilor a polyethylene glycol. Various other materials may be present ascoatings or to otherwise modify the physical form of the solid unitdosage form. For instance, tablets, pills, or capsules may be coatedwith gelatin, wax, shellac or sugar and the like. A syrup or elixir maycontain the active compound, sucrose or fructose as a sweetening agent,methyl and propylparabens as preservatives, a dye and flavoring such ascherry or orange flavor. Of course, any material used in preparing anyunit dosage form should be pharmaceutically acceptable and substantiallynon-toxic in the amounts employed. In addition, the active compound maybe incorporated into sustained-release preparations and devices.

The active compound may also be administered intravenously orintraperitoneally by infusion or injection. Solutions of the activecompound or its salts can be prepared in water, optionally mixed with anontoxic surfactant. Dispersions can also be prepared in glycerol,liquid polyethylene glycols, triacetin, and mixtures thereof and inoils. Under ordinary conditions of storage and use, these preparationscontain a preservative to prevent the growth of microorganisms.

The pharmaceutical dosage forms suitable for injection or infusion caninclude sterile aqueous solutions or dispersions or sterile powderscomprising the active ingredient which are adapted for theextemporaneous preparation of sterile injectable or infusible solutionsor dispersions, optionally encapsulated in liposomes. In all cases, theultimate dosage form should be sterile, fluid and stable under theconditions of manufacture and storage. The liquid carrier or vehicle canbe a solvent or liquid dispersion medium comprising, for example, water,ethanol, a polyol (for example, glycerol, propylene glycol, liquidpolyethylene glycols, and the like), vegetable oils, nontoxic glycerylesters, and suitable mixtures thereof The proper fluidity can bemaintained, for example, by the formation of liposomes, by themaintenance of the required particle size in the case of dispersions orby the use of surfactants. The prevention of the action ofmicroorganisms can be brought about by various antibacterial andantifungal agents, for example, parabens, chlorobutanol, phenol, sorbicacid, thiomersal, and the like. In many cases, it will be preferable toinclude isotonic agents, for example, sugars, buffers or sodiumchloride. Prolonged absorption of the injectable compositions can bebrought about by the use in the compositions of agents delayingabsorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the activecompound in the required amount in the appropriate solvent with variousof the other ingredients enumerated above, as required, followed byfilter sterilization. In the case of sterile powders for the preparationof sterile injectable solutions, the preferred methods of preparationare vacuum drying and the freeze drying techniques, which yield a powderof the active ingredient plus any additional desired ingredient presentin the previously sterile-filtered solutions.

For topical administration, the present compounds may be applied in pureform, i.e., when they are liquids. However, it will generally bedesirable to administer them to the skin as compositions orformulations, in combination with a dermatologically acceptable carrier,which may be a solid or a liquid.

Useful solid carriers include finely divided solids such as talc, clay,microcrystalline cellulose, silica, alumina and the like. Useful liquidcarriers include water, alcohols or glycols or water-alcohol/glycolblends, in which the present compounds can be dissolved or dispersed ateffective levels, optionally with the aid of non-toxic surfactants.Adjuvants such as fragrances and additional antimicrobial agents can beadded to optimize the properties for a given use. The resultant liquidcompositions can be applied from absorbent pads, used to impregnatebandages and other dressings, or sprayed onto the affected area usingpump-type or aerosol sprayers.

Thickeners such as synthetic polymers, fatty acids, fatty acid salts andesters, fatty alcohols, modified celluloses or modified mineralmaterials can also be employed with liquid carriers to form spreadablepastes, gels, ointments, soaps, and the like, for application directlyto the skin of the user.

Examples of useful dermatological compositions which can be used todeliver the compounds of formula I to the skin are known to the art; forexample, see Jacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat.No. 4,992,478), Smith et al. (U.S. Pat. No. 4,559,157) and Wortzman(U.S. Pat. No. 4,820,508).

Useful dosages of the compounds of formula I can be determined bycomparing their in vitro activity, and in vivo activity in animalmodels. Methods for the extrapolation of effective dosages in mice, andother animals, to humans are known to the art; for example, see U.S.Pat. No. 4,938,949.

Generally, the concentration of the compound(s) of formula I in a liquidcomposition, such as a lotion, will be from about 0.1-25 wt-%,preferably from about 0.5-10 wt-%. The concentration in a semi-solid orsolid composition such as a gel or a powder will be about 0.1-5 wt-%,preferably about 0.5-2.5 wt-%.

The amount of the compound, or an active salt or derivative thereof,required for use in treatment will vary not only with the particularsalt selected but also with the route of administration, the nature ofthe condition being treated and the age and condition of the patient andwill be ultimately at the discretion of the attendant physician orclinician.

In general, however, a suitable dose will be in the range of from about0.5 to about 100 mg/kg, e.g., from about 10 to about 75 mg/kg of bodyweight per day, such as 3 to about 50 mg per kilogram body weight of therecipient per day, preferably in the range of 6 to 90 mg/kg/day, mostpreferably in the range of 15 to 60 mg/kg/day.

The compound is conveniently administered in unit dosage form; forexample, containing 5 to 1000 mg, conveniently 10 to 750 mg, mostconveniently, 50 to 500 mg of active ingredient per unit dosage form.

Ideally, the active ingredient should be administered to achieve peakplasma concentrations of the active compound of from about 0.5 to about75 μM, preferably, about 1 to 50 μM, most preferably, about 2 to about30 μM. This may be achieved, for example, by the intravenous injectionof a 0.05 to 5% solution of the active ingredient, optionally in saline,or orally administered as a bolus containing about 1-100 mg of theactive ingredient. Desirable blood levels may be maintained bycontinuous infusion to provide about 0.01-5.0 mg/kg/hr or byintermittent infusions containing about 0.4-15 mg/kg of the activeingredient(s).

The desired dose may conveniently be presented in a single dose or asdivided doses administered at appropriate intervals, for example, astwo, three, four or more sub-doses per day. The sub-dose itself may befurther divided, e.g., into a number of discrete loosely spacedadministrations; such as multiple inhalations from an insufflator or byapplication of a plurality of drops into the eye.

The ability of a compound of the invention to effect topoisomerase Imediated DNA cleavage can be determined using pharmacological modelsthat are well known to the art, for example, using a model like Test Adescribed below.

Test A. Topoisomerase I Cleavage Assay.

Representative compounds of the invention were evaluated in a cleavageassay using recombinant topoisomerases I. This assay was preformed asdescribed by B. Gatto et al. Cancer Res., 1996, 56, 2795-2800. Humantopoisomerase I was isolated as a recombinant fusion protein using a T7expression system. Plasmid YEpG was purified by the alkali lysis methodfollowed by phenol deproteination and CsCl/ethidium isopycniccentrifiigation as described by Maniatis, T.; Fritsch, E. F.; Sambrook,J. Molecular Cloning, a Laboratory Manual; Cold Spring HarborLaboratory: Cold Spring Harbor, N.Y. 1982; pp 149-185. The end-labelingof the plasmid was accomplished by digestion with a restriction enzymefollowed by end-filling with Klenow polymerase as previously describedby Liu, L. F.; Rowe, T. C.; Yang, L.; Tewey, K. M.; Chen, G. L.“Cleavage of DNA by mammalian topoisomerase II,” J. Biol. Chem. 1983,258, 15365. IC₅₀ values were calculated after 4 days of continuous drugexposure. Topoisomerase I cleavage values are reported as REC, RelativeEffective Concentration (i.e., concentrations relative to compound 5,whose value is arbitrarily assumed as 1) that is able to produce thesame cleavage on the plasmid DNA in the presence of human topoisomeraseI.

The cytotoxic effects of a compound of the invention can be determinedusing pharmacological models that are well known to the art, forexample, using a model like Test B described below.

Test B. Cytotoxicity Assay.

Cytotoxicity was determined using the MTT-microtiter plate tetrazoliniumcytotoxicity assay (MTA) (See Chen A. Y. et al. Cancer Res. 1993, 53,1332; Mosmann, T. J., J. Immunol. Methods 1983, 65, 55; and Carmichael,J. et al. Cancer Res. 1987, 47, 936). The human lymphoblast RPMI 8402and its camptothecin-resistant variant cell line, CPT-K5 were providedby Dr. Toshiwo Andoh (Aichi Cancer Center Research Institute, Nagoya,Japan) (see Andoh, T.; Okada, K. “Drug resistance mechanisms oftopoisomerase I drugs,” Adv. in Pharmacology 1994, 29B, 93. Thecytotoxicity assay was performed using 96-well microtiter plates. Cellswere grown in suspension at 37° C. in 5% CO₂ and maintained by regularpassage in RPMI medium supplemented with 10% heat- inactivated fetalbovine serum, L-glutamine (2 mM), penicillin (100 U/mL), andstreptomycin (0.1 mg/mL). For determination of IC₅₀, cells were exposedcontinuously with varying concentrations of drug and MTT assays wereperformed at the end of the fourth day.

Data from Test A and Test B is shown in FIG. 2 for representativecompounds of the invention.

Compounds of formula I are potent topoisomerase I poisons. Additionally,compounds of formula I exhibit cytotoxic activity against RPMI 8402cancer cells and camptothecin resistant CPT-K5 cells. Accordingly,compounds of formula I are useful as cytotoxic agents, for the treatmentof cancers, and in particular, solid mammalian tumors or hematologicmalignancies. Compounds of the invention are also useful aspharmacological tools for in vitro and in vivo study of topoisomerasefunction and activity.

As used herein, the term “solid mammalian tumors” includes cancers ofthe head and neck, lung, mesothelioma, mediastinum, esophagus, stomach,pancreas, hepatobiliary system, small intestine, colon, rectum, anus,kidney, ureter, bladder, prostate, urethra, penis, testis, gynecologicalorgans, ovarian, breast, endocrine system, skin central nervous system;sarcomas of the soft tissue and bone; and melanoma of cutaneous andintraocular origin. The term “hematological malignancies” includeschildhood leukemia and lymphomas, Hodgkin's disease, lymphomas oflymphocytic and cutaneous origin, acute and chronic leukemia, plasmacell neoplasm and cancers associated with AIDS. The preferred mammalianspecies for treatment are humans and domesticated animals.

The compounds are also expected to exhibit some of the otherbioactivities observed for topoisomerase inhibitors, such asantibacterial, antifungal, antiprotozoal, antielmintic and/or antiviralactivity. In particular, the compounds may exhibit antifungal activity.Thus, the invention also provides a therapeutic method to treat fungalinfection comprising administering to a mammal afflicted with a fungalinfection, an effective antifungal amount of a compound of the formulaI, or a pharmaceutically acceptable salt thereof.

The invention will now be illustrated by the following non-limitingExamples, wherein unless otherwise stated: melting points weredetermined with a Thomas-Hoover Unimelt capillary melting pointapparatus; column chromatography refers to flash chromatographyconducted on SiliTech 32-63 μm, (ICN Biomedicals, Eschwegge, Ger.) usingthe solvent systems indicated; infrared spectral data (IR) were obtainedon a Perkin-Elmer 1600 Fourier transform spectrophotometer and arereported in cm⁻¹; proton (¹H NMR) and carbon (¹³C NMR) nuclear magneticresonance were recorded on a Varian Gemini-200 Fourier Transformspectrometer; NMR spectra (200 MHZ ¹H and 50 MHZ ¹³C) were recorded inthe deuterated solvent indicated with chemical shifts reported in δunits downfield from tetramethylsilane (TMS); coupling constants arereported in hertz (Hz); mass spectra were obtained from WashingtonUniversity Resource for Biomedical and Bio-organic Mass Spectrometrywithin the Department of Chemistry at Washington University, St. Louis,Mo.; and combustion analyses were performed by Atlantic Microlabs, Inc.,Norcross, Ga., and were within ±0.4% of the theoretical value.

EXAMPLES Example 15-Phenyl-2-[2′(2″-hydroxybenzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(2).

5-Phenyl-2-[2′-(3,4-diaminophenyl)benzimidazol-5′yl]benzimidazole, (29.7mg, 0.07 mmol) and urea (6 mg, 0.1 mmol) were dissolved in DMF (0.4 ml).The mixture was refluxed at 150° C. for 7 hours. The cooled reactionmixture when concentrated in vacuo and washed with water provided 27.6mg (88%) of pure yellow solid; mp>280° C.; IR (KBr) 3382, 3133, 1693,1475, 1444, 1279; ¹H NMR (DMSO-d₆ +3 drops CF₃COOH) δ 7.3 (d,1H,J=8.14),7.46-7.80 (m,3H), 7.80 (d,2H,J=8.1), 7.89-8.01(m,4H), 8.05-8.14 (m,2H),8.32 (d,1H,J=8.34), 8.63 (s,1H), 11.35 (s,1H); ¹³C NMR (DMSO-d₆+3 dropsCF₃COOH) δ 108.07, 109.55, 111.78, 114.03, 114.57, 114.62, 115.3,120.21, 122.53, 125.45, 125.82, 127.42, 128.1, 129.26, 130.81, 131.59,132.66, 132.87, 135.15, 135.33, 139.20, 139.61, 149.32, 153.14, 155.71;HRMS (FAB) calculated for C₂₇H₁₉N₆(MH⁺) 443.1620 found 443.1625.

The intermediate5-phenyl-2-[2′-(3,4-diaminophenyl)benzimidazol-5′yl]benzimidazole wasprepared as follows.

a. 5-Phenyl-2-[2′-(3,4diaminophenyl)benzimidazol-5′-yl]benzimidazole. Asolution of5-phenyl-2-[2′-(3,4-dinitrophenyl)benzimidazol-5′yl]benzimidazole (75mg, 0.16 mmol) in ethyl acetate (50 mL) was reduced by hydrogenationover 10% Pd/C (15 mg) for 90 minutes. The resulting solution was passedthrough a bed of Celite and the ethyl acetate was removed to give thediamine, which was used without further purification.

The starting5-phenyl-2-[2′-(3,4-dinitrophenyl)benzimidazol-5′yl]benzimidazole can beprepared as described by J. S. Kim et al. J. Med. Chem. 1997, 40,2818-2824.

Example 25-Phenyl-2-[2′-(2″-mercaptobenzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(3).

5-Phenyl-2-[2′-(3,4-diaminophenyl)benzimidazol-5′yl]benzimidazole, (59.4mg, 0.14 mmol) and ethylxanthic acid potassium salt (25.1 mg, 0.16 mmol)were refluxed in ethanol (1 ml) and distilled water (0.1 ml) overnight.The cooled reaction mixture was acidified to pH 3 with glacial aceticacid, volume condensed in vacuo and purified directly by columnchromatography. Elution with (40-100%) ethyl acetate/n-hexanes provided69% of yellow solid; mp>280° C.; IR (KBr) 3089, 2926, 2851, 1712, 1624,1549, 1449, 1380, 1274, 1186, 1079; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ7.33-7.42 (m,2H), 7.48-7.63 (t,4H), 7.71-7.82 (m,4H), 7.89 (s,1H),8.04-8.06 (m,1H), 8.1-8.24 (m,1H), 8.42 (d,1H,J=2.4); ¹³C NMR (DMSO-d₆+3drops CF₃COOH) δ 107.37, 107.15, 109.2, 109.68, 111.81, 111.73, 113.31,113.53, 114.57, 114.64, 114.68, 115.56, 125.26, 127.44, 128.16, 129.33,131.64, 132.93, 133.27, 139.1, 136.61, 139.62, 149.51, 152.94, 171.13;HRMS (FAB) calculated for C₂₇H₁₉N₆S (MH⁺) 459.1392, found 459.1403.

Example 35-Phenyl-2-[2′-(2″-aminobenzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(4).

5-Phenyl-2-[2′-(3,4-diaminophenyl)benzimidazol-5′yl]benzimidazole, (66mg, 0.16 mmol) was dissolved in DMF (0.2 ml) and methanol (1 ml), andwas added to cyanogen bromide (10% solution in water, 0.33 ml, 0.63mmol). The reaction mixture was stirred overnight at room temperature.The mixture was concentrated under reduced pressure. Compound wasrecrystallized from methanol to give 47% of pale brown solid; mp>280°C.; IR (KBr) 3352, 3052, 2926, 1680, 1624, 1574, 1461, 1261,679; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 7.46-7.62 (m,3H), 7.79 (d,2H,J=7.26),7.87-7.96 (m,2H), 7.99-8.01 (m,2H), 8.20-8.26 (m,2H), 8.31 (s,1H), 8.72(d,2H,J=9.12); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 107.38, 110.89,111.75, 111.78, 114.67,115.13, 115.24, 115.92, 123.59, 125.58, 126.84,127.5, 127.53, 127.57, 127.76, 128.2, 129.43, 130.86, 131.87, 133.13,138.74, 139.74, 150.10, 152.14, 153.42; HRMS (FAB) calculated forC₂₇H₂₀N₇ (MH⁺) 442.1780 found 442.1776.

Example 45-Phenyl-2-[2′(2″-trifluoromethylbenzimidazol-5″yl)benzimidazol-5′-yl]benzimidazole(5).

5-Phenyl-2-[3,4-diaminophenyl]benzimidazole (0.160 g, 0.53 mmol) washeated with 5-formyl-2-trifluoromethylbenzimidazole (0.12 g, 0.54 mmol)in nitrobenzene (4 mL) at 145° C. overnight. Nitrobenzene was removedusing a Kugelrohr and the compound purified by column chromatography.(1-16%) methanol/ethyl acetate provided 40% pure yellow compound;mp>280° C.; IR (KBr) 3047, 2927, 1698, 1626, 1543, 1440, 1287, 1158; ¹HNMR (DMSO-d₆+3 drops CF₃COOH)δ 7.44-7.59 (m,3H), 7.79 (d,2H,J=7.04),7.87-8.01 (m,2H), 8.05-8.09 (m,2H), 8.15-8.19 (m,1H), 8.29-8.35 (m,2H),8.70 (m,2H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 111.79, 114.68, 114.92,115.85, 117.53, 117.58, 118.37, 118.41, 119.58, 120.46, 124.14, 124.79,125.71, 125.74, 127.47, 128.18, 129.36, 131.73, 132.99, 134.93, 137.44,138.97, 139.02, 139.07, 139.66, 140.34, 149.81, 153.46; HRMS (FAB)calculated for C₂₈H₁₈N₆F₃ (MH⁺) 495.1545 found 495.1543.

The intennediate 5-formyl-2-trifluoromethylbenzimidazole was prepared asfollows.

a. 3,4-Diaminobenzonitrile. 4-Amino-3-nitrobenzonitrile (3 g, 18.4 mmol)in ethyl acetate (120 ml) was reduced by hydrogenation using 45 psi ofH₂ and 10% Pd-C (300 mg) for 1.5 hr. After passing through a bed ofcelite, the solvent was removed in vacuo and 2.43 g (99%) of white solidwas obtained; mp 144-145° C.; IR (KBr) 3431, 2726, 2211, 1861, 1631,1311, 1149, 722; ¹H NMR (CDCl₃) δ 3.18-3.87 (brs, 4H),6.68 (d, 1H,J=8.06), 6.94 (d,1H,J=1.74), 7.02-7.27 (dd,1H,J=1.78, 8.06); ¹³C NMR(CDCl₃) δ 100.27, 115.86, 119.52, 122.19, 125.66, 135.94, 142.52; Thecrude diamine obtained was typically used without further purification.

b. 5-Cyano-2-trifluoromethylbenzimidazole. 3,4 Diaminobenzonitrile (200mg, 1.5 mmol) was refluxed with trifluoroacetic acid (0.3 ml) for 6hours. The mixture was neutralized with 2 N NaOH and extracted withethyl acetate. The ethyl acetate layer was dried over anhydrous Na₂SO₄.Column with (0-10%) ethyl acetate/n-hexanes gave 88% of pure whitecompound; mp 182-183° C.; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 7.72-7.77(1H,dd,J=1.46,8.56), 7.88 (d,1H, 8.42), 8.35 (s,1H); ¹³C NMR (DMSO-d₆+3drops CF₃COOH) δ 106.47, 106.64, 112.36, 117.31, 118.09, 119.44, 123.53,123.81, 127.47; Anal. calculated for C₉H₄N₃F₃: C; 51.20, H; 1.91, N;19.90, found C; 51.45, H; 2.03, N; 19.68.

c. 5-Formyl-2-trifluoromethylbenzimidazole.5-Cyano-2-trifluoromethyl-benzimidazole (196 mg, 0.93 mmol) was refluxedwith HCOOH (14 ml), H₂O (5 ml) and Ni-Al (0.9 g) catalyst for 6 hours.The hot reaction mixture was filtered through celite and concentrated invacuo. The solution was basified with 2N NaOH. Extraction with ethylacetate followed by drying over anhydrous sodium sulfate andconcentration of the ethyl acetate layer in vacuo gave the crudealdehyde. Purification was achieved by column chromatography. Elutionwith 10/90 ethyl acetate/n-hexanes gave 41% of pure white compound; mp178-179° C.; IR (KBr) 3210, 2737, 1699, 1552, 1328, 1187 (d), 986; ¹HNMR (DMSO-d₆+3 drops CF₃COOH) δ 7.87-7.95 (m, 2H), 8.34(s,1H), 10.11(s,1H).¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 106.63, 112.35, 116.72,118.08, 121.87, 123.80, 124.04, 132.95, 192.65; HRMS (EI) calculated forC₉H₅N₂OF₃ m/z 214.0354 found 214.0348.

The intermediate 4-amino-3-nitrobenzonitrile used in subpart a above iscommercially available (Aldrich Chemical Company)

The intermediate 5-phenyl-2-[3,4-diaminophenyl]benzimidazole wasprepared as follows.

d. 5-Phenyl-2-[3,4-diaminophenyl]benzimnidazole.5-Phenyl-2-[3,4-nitrophenyl]benzimidazole (580 mg, 1.6 mmol) wasdissolved in 100 ml ethyl acetate and hydrogenation was carried outusing 10% Pd/C (100 mg) for 1.5 hours. The reaction mixture was passedthrough a bed of celite and the bed washed with methanol. The washingswere concentrated in vacuo to yield (477 mg, 1.59 mmol) of the crudediamine in 98% yield. The diamine was not characterized but used withoutpurification; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 4.70 (brs,2H), 4.96(brs, 2H), 6.62 (d,1H,8.02), 7.37 (m,8H), 7.53 (m,2H).

Example 55-Phenyl-2-[2′-(2″-hydroxymethylbenzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(7).

5-Phenyl-2-[3,4-diaminophenyl]benzimidazole (178 mg, 0.6 mmol) and5-formyl-2-hydroxymethyl benzimidazole (104.2 mg, 0.6 mmol) werecondensed in nitrobenzene (10 ml) overnight at 145° C. Nitrobenzene wasremoved from the reaction mixture with a Kugelrohr and the compound waspurified directly by column chromatography. Elution with (1-18%)methanol/ethyl acetate provided 62% of yellow solid; mp>280° C.; IR(Nujol) 3406, 2922, 2725, 1631, 1553, 1461, 1377; ¹H NMR (DMSO-d₆+3drops CF₃COOH) δ 5.1 (s,2H), 7.45-7.59 (m,3H), 7.79 (d,2H,J=6.96),8.23-8.28 (m,1H), 8.47 (d,1H, J=8.59), 8.68 (s,2H); ¹³C NMR (DMSO-d₆+3drops CF₃COOH) δ 55.80, 111.69, 113.68, 114.59, 115.32, 115.77, 116.21,118.31, 123.77, 124.52, 125.21, 125.61, 127.47, 127.49, 127.54, 128.14,129.38, 131.64, 131.89, 132.91, 133.54, 137.66, 138.86, 139.68, 140.13,150.25, 153.37, 157.62; HRMS (FAB) calculated for C₂₈H₂₁N₆O (MH⁺)457.1777 found 457.1774.

The intermediate 5-formyl-2-hydroxymethyl benzimidazole was prepared asfollows.

a. 5-Cyano-2-hydroxymethylbenzimidazole. 3,4 Diaminobenzonitrile (0.2 g,1.50 mmol) was heated with glycolic acid (0.18 g, 2.37 mmol) in HCl (1.5ml of 4N) for 2 hours. After neutralization with 2M sodium carbonate theproduct was extracted into ethyl acetate, dried over anhydrous Na₂SO₄and concentrated in vacuo to give a white colored solid. The compoundwas purified by column chromatography. Elution with (75-100%) ethylacetate/n-hexanes gave 65.5% (133 mg, 0.76 mmol) of pure compound; mp172-173° C.; IR (Nujol) 3350, 2928, 2219, 1621, 1536, 1302, 1217, 1036,815; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 4.88 (s,2H), 7.52-7.57(dd,1H,J=1.46,8.38), 7.69 (d,1H,J=8.36), 7.95 (s,1H), ¹³C NMR (DMSO-d₆+3drops CF₃COOH) δ 55.81, 107.99, 115.68, 118.64, 119.50, 129.00, 131.50,134.39; HRMS (El) calculated for C₉H₇N₃O (m/z) 173.0590 found 173.0590.

b. 5-Formyl-2-hydroxymethylbenzimidazole. Ni-Al (1.2 g) was added to asolution of 5-cyano-2-hydroxymethylbenzimidazole (0.17 g, 0.97 mmol) inHCOOH (17 ml) and water (1.6 ml). The reaction mixture was heated at 95°C. for 5 hours. The hot mixture was filtered through a bed of celite andthe reaction flask and the celite bed rinsed with water and thenmethanol. The combined solution was concentrated in vacuo. Afteraddition of water to this residue, a white precipitate was formed. ThepH of this suspension was adjusted to 9 by dropwise addition of 2N NaOH.The product was obtained by extraction with ethyl acetate. The ethylacetate extract was dried over anhydrous Na₂SO₄ and concentrated invacuo to give a pure white product (61% yield); mp 189-190° C.; IR (KBr)3309, 2924, 1674, 1619, 1434, 1291, 1073, 808; ¹H NMR (DMSO-d₆+3 dropsCF₃COOH) δ 5.07 (s,2H), 7.94 (d,1H,J=8.68), 8.04-8.09(dd,1H,J=1.34,8.51), 8.32 (s,1H), 10.4 (s,1H); ¹³C NMR (DMSO-d₆+3 dropsCF₃COOH) δ 55.76, 114.95, 116.81, 126.03, 131.45, 133.89, 135.11,192.31; HRMS (EI) calculated for C₉H₈N₂O m/z 176.0586 found 176.0586.

Example 65-Phenyl-2-[2′-[2″-[2-(N-benzoyl)aminomethyl]benzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(8).

5-Phenyl-2-[3,4-diaminophenyl]benzimidazole (75 mg, 0.25 mmol) and5-formyl-2-[(N-benzoyl)aminomethyl]benzimidazole (70 mg, 0.25 mmol,)were heated in nitrobenzene (6 ml) at 145° C. overnight. Nitrobenzenewas removed with a Kugelrohr and the compound was loaded on a column.(2-20%) methanol/ethyl acetate gave 45% yellowish compound; mp>280° C.;IR (KBr) 3204, 1637, 1542, 1442, 1384, 1292, 1026, 818; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 7.46-7.66 (m,6H), 7.80 (d, 2H, J=7.06),7.87-8.1 (m, 7H), 8.21-8.25 (m,1H), 8.43-8.48 (m,1H), 8.67 (s,2H); ¹³CNMR (DMSO-d₆+3 drops CF₃COOH) δ 36.65, 107.37, 111.73, 114.53, 114.58,115.26, 115.49, 116.01, 119.47, 122.49, 124.81, 125.56, 126.72, 127.41,127.83, 128.04, 128.07, 128.54, 129.25, 131.56, 131.87, 132.12, 132.84,133.17, 134.11, 136.21, 137.76, 139.08, 139.66, 149.67, 152.62, 155.64,167.60; HRMS (FAB) calculated for C₃₅H₂₆N₇O (MH⁺) 560.2199 found560.2209.

The intermediate 5-formyl-2-[(N-benzoyl)aminomethyl]benzimidazole wasprepared as follows.

a. 5-Cyano-2-[(N-benzoyl)aminomethyl]benzimidazole.3,4-Diaminobenzonitrile (250 mg, 1.88 mmol) was finely ground in amortar with (0.34 g, 1.9 mmol) hippuric acid and intimately mixed andthen carefully fused for 3 hours. The temperature was then raised to160° C. when water was evolved as bubbles. After cooling the glassy masswas dissolved in ethyl acetate and purified by column chromatography.(50-100%) ethyl acetate/n-hexanes yielded 86% of pale buff coloredcompound; mp 131-132° C.; IR (Nujol) 2826, 2221, 1635, 1313, 1019, 814;¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 4.97 (d,2H,J=5.22), 7.52-7.61 (m,3H),7.91-7.99 (m,4H), 8.37 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ36.80, 107.73, 115.72, 118.81, 119.67127.83, 128.61, 128.64, 128.67,128.78, 132.15, 132.20, 13322, 135.01, 156.13, 167.51; HRMS (EI)calculated for C₁₆H₁₂N₄O m/z 276.1011 found 276.1012.

b. 5-Formyl-2-[(N-benzoyl)aminomethyllbenzimidazole.5-Cyano-2-[(N-benzoyl)aminomethyl]benzimidazole (0.33 g, 1.2 mmol) wasdissolved in formic acid (18 ml). Water (5 ml) and Ni-Al (1.14 g) wereadded to it. The mixture was heated under nitrogen at 95° C. for 6 hoursand while hot passed through a celite bed. The bed was washed withmethanol and the washings concentrated in vacuo. The pH of the solutionwas adjusted with 2N NaOH to 9.0 and extracted with ethyl acetate. Theextractions were dried over anhydrous Na₂SO₄ and concentrated in vacuo.The residue was purified over column chromatography using (50-100%)ethyl acetate/n-hexanes to give 26% of pure cream colored product; mp108-109° C.; IR (KBr) 3314, 2933, 1687, 1646, 1539, 1289, 806; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 4.99 (d,1H,J=5.12), 7.54-7.63 (m,4H),7.93-8.07 (m,3H), 8.34 (s,1H), 10.15 (s,1H); ¹³C NMR (DMSO-d₆+3 dropsCF₃COOH) δ 36.83, 115.10, 117.18, 125.80, 127.85, 128.71, 132.26,132.33, 133.2, 133.68, 155.77, 167.54, 192.54; HRMS (EI) calculated forC₁₆H₁₃N₃O₂ m/z 279.1008 found 279.1003.

Example 75-Phenyl-2-[2′-[2″-(2-hydroxyethyl)benzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(10)

5-Phenyl-2-[2′-[2″-(2-methoxyethyl)benzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(30 mg, 0.06 mmol, Example 10) was suspended in freshly distilled ethylacetate (30 ml) to which was added 10 equivalence of BBr₃ (0.62 ml,1.0M) at −78° C. After stirring at room temperature overnight, thereaction was quenched by adding water (10 ml). The mixture was basifiedto pH 9.0 with ammonium hydroxide and extracted with ethyl acetate anddried over anhydrous Na₂SO₄. The crude mixture was separated on achromatotron, (0-30%) methanol/ethyl acetate to give 10.6 mg of theproduct in 33% yield as a brown solid. mp>280° C.; IR (KBr) 3401, 3150,2876, 1632, 1540, 1442, 1388, 1268, 1013, 823; ¹H NMR (DMSO-d₆+3 dropsCF₃COOH) δ 3.35 (t,2H), 3.98 (t,2H), 7.42-7.56 (m,3H), 7.76(d,2H,J=7.7), 7.85-7.98 (m,2H), 8.06-8.19 (m,3H), 8.33 (d,1H, J=8.5),8.44 (d,1H, J=8.8), 8.73 (s,2H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ30.75, 58.09, 111.71, 114.36, 114.53, 115.28, 115.98, 116.02,118.28,119.43, 122.37, 124.71, 124.76, 125.43, 125.73, 127.40, 128.1,129.25, 131.55, 131.64, 132.83, 133.95, 135.26, 137.79, 139.06, 139.64,149.67, 152.63, 156.21; HRMS (FAB) calculated for C₂₉H₂₃N₆O (MH⁺)471.1933 found 471.1935.

Example 85-Phenyl-2-[2′-[2″-(2-aminoethyl)benzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(11)

5-Phenyl-2-[2′-[2″-(2-acetamidoethyl)benzinidazol-5″-yl)]benzimidazol-5′-yl]benzimidazole(35 mg, 0.07 mmuyol, Example 9) was hydrolyzed with 2N HCl (5 ml) at110° C. for 3 hours. The cooled reaction mixture was basified witharnmonium hydroxide to pH 9.0 and purified by column chromatography.Elution with 50:50 methanol/ethyl acetate provided 75% yellow solid;mp>280° C.; IR (Nujol) 3375, 2719, 1553, 1461,1377; ¹H NMR (DMSO-d₆+3drops CF₃COOH) δ 3.45-3.52 (m,4H), 7.45-7.56 (m,2H), 7.79(d, 2H,J=7.04), 7.88-8.00 (m,2H), 8.07-8.27 (m,5H),8.42 (d,1H, J=8.92), 8.68(d,2H,J=4.76); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 25.52, 36.36, 111.74,113.77, 114.62, 115.33, 115.76, 116.17, 118.33, 123.75, 123.94, 124.75,125.61, 127.48, 128.16, 129.39, 131.71, 132.98, 133.11, 134.77, 137.73,138.84, 139.71, 140.12, 150.34, 153.43, 153.61; HRMS (FAB) calculatedfor C₂₇H₁₉N₆O (MH⁺) 470.2093 found 470.2089.

Example 95Phenyl-2-[2′-(2″(2-acetamidoethyl)benzimidazol-5″-yl)]benzimidazol-5′-yl]benzimidazole (12).

5-Phenyl-2-[3,4-diaminophenyl]benzimidazole (124 mg, 0.41 mmol) and5-formyl-2-(2-acetamidoethyl)benzimidazole (95 mg, 0.41 mmol) werecondensed in nitrobenzene (7 ml) overnight at 145° C. Nitrobenzene wasremoved with the aid of a Kugelrohr and the compound purified directlyby flash column chromatography. Elution with (1-15 %) methanol/ethylacetate provided 69% of yellow solid; mp>280° C.; IR (KBr) 3064, 2954,2862, 1654, 1556, 1442, 1286; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 1.81(s,3H), 3.18-3.35 (m,2H), 3.61-3.64 (m,2H), 7.45-7.6 (m,3H), 7.79(d,2H,J=7.04 ), 7.87-8.00 (m,2H), 8.07-8.30 (m,4H), 8.46 (d,1H,J=8.5),8.71 (s,2H); ¹³C NMR (DMSO-d₆3 drops CF₃COOH) δ 22.59, 27.89, 36.41,111.73, 113.66, 114.59, 115.22, 115.69, 116.17, 118.61, 124.04, 125.22,125.66, 127.47, 127.56, 128.14, 128.18, 129.36, 131.62, 131.84, 132.89,133.69, 137.10, 138.94, 139.54, 139.68, 150.16, 153.24, 155.40, 158.47,170.27; HRMS (FAB) calculated for C₃₁H₂₅N₇O (MH⁺) 512.2199 found512.2201.

The intermediate 5-formyl-2-(2-acetamidoethyl)benzimidazole was preparedas follows.

a. 5-Cyano-2-(2-aminoethyl)benzimidazole. A solution of 3,4diaminobenzonitrile (1 g, 7.52 mmol) and β-alanine (1.0 g, 11.3 mmol) inHCl (8 ml, 6N) was refluxed for 24 hrs. At this time the diamine wasbarely detectable by TLC. After neutralization with 2N NaOH, thecompound was directly loaded on the column. Elution with (75-100%) ethylacetate/n-hexanes and further with (1-25%) methanol/ethyl acetate gave46% (0.65 g) of pure yellow compound; mp 105-106° C.; IR (KBr) 3438,2855, 2734, 2212, 1625, 1569, 1483, 1457, 1385, 1222, 1153; ¹H NMR(CD₃OD) δ 3.09-3.13 (m,4H), 7.49-7.66 (m,2H), 7.91 (d,1H,J=1.46); ¹³CNMR (CD₃OD) δ 33.13, 40.99, 106.27, 116.57, 121.04, 121.19, 127.08,140.40, 142.59, 158.82; HRMS (EI) calculated for C₁₀H₁₀N₄ m/z 186.0905found 186.0906.

b. 5-Cyano-2-(2-acetamidoethyl)benzimidazole.5-Cyano-2-(2-aminoethyl)benzimidazole (0.4 g, 2.15 mmol) was refluxed indry THF (10 ml), acetic anhydride (0.4 ml) and triethylamine (0.4 ml)for 4 hrs. The mixture was neutralized with 2N NaOH and extracted withethyl acetate to give the crude acetamide. The acetamide was purifiedusing flash column chromatography. Elution with (0-15%) methanol/ethylacetate gave 70% of pure white compound; mp 218-219° C.; IR (KBr) 3233,3053, 2225, 1653, 1573, 1442, 1374, 1303, 1058, 815; ¹H NMR (DMSO-d₆+3drops CF₃COOH) δ 1.78 (s,3H), 3.26 (t,2H), 3.53-3.62 (2H, J=6.45,12.38), 7.89-7.95 (dd, 1H, J=1.42, 8.48), 8.00 (d, J=8.22,1H), 8.19(t,1H), 8.45 (d,1H,J=1.42); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 22.57,27.82, 36.71, 108.06, 115.52, 118.62, 119.33, 129.02, 131.29, 134.26,156.23, 170.18; Anal. calculated for C₁₂H₁₂N₄O.¼H2O: C; 61.92, H; 5.41,N; 24.07 found C; 62.60, H; 5.41, N; 23.82.

c. 5-Formyl-2-(2-acetamidoethyl)benzimidazole.5-Cyano-2-(2-acetamidoethyl)benzimidazole (94.6 mg, 0.41 mmol) wasrefluxed in HCOOH (5.9 ml), water (0.5 ml) and Ni-Al (0.4 g) catalystfor six hours . The mixture was filtered hot through celite and the bedwashed with methanol. The washings were concentrated in vacuo. Theconcentrate was basified with 2N NaOH to pH 9 and extracted with ethylacetate. The ethyl acetate layer was dried over anhydrous Na₂SO₄ andpurified by flash column chromatography. (0-15%) methanol/ethyl acetategave 80% (70.10 mg) of pure white product; mp 220-221° C.; IR (KBr)3222, 3047, 1656, 1575, 1439, 1289, 1110, 1058, 816; ¹H NMR (DMSO-d₆+3drops CF₃COOH) δ 1.79 (s,3H), 3.29 (t, 2H), 3.54-3.64 (q, J=6.66, 12.64,2H), 7.97-8.09 (m,2H), 8.19 (t,1H), 8.38 (s, 1H), 10.17 (s,1H); ¹³C(DMSO-d₆+3 drops CF₃COOH) δ 22.69, 27.91, 36.75, 114.89, 116.86, 125.84,131.67, 133.81, 135.33, 155.88, 170.13, 192.47; Anal. calculated forC₁₂H₁₃N₃O: C; 62.32, H; 5.67, N; 18.17 found C; 62.10, H; 5.7, N; 17.92.

Example 105-Phenyl-2-[2′-[2″-(2-methoxyethyl)benzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(13)

5-Phenyl-2-[3,4-diaminophenyl]benzimidazole (0.17 mg, 0.58 mmol) and5-formyl-2-(2-methoxyethyl)benzimidazole (120 mg, 0.59 mmol) were heatedtogether in of nitrobenzene (5 ml) for 15 hours at 145° C. Nitrobenzenewas removed with a Kugelrohr and the compound was loaded onto a column.(1-12%) methanol/ethyl acetate gave 80% pure yellowish product; mp>280°C.; IR (KBr) 3157, 2933, 1629, 1551, 1441, 1385, 1288, 1108, 818, 760,698; ¹H NMR (DMSO-d₆+3drops CF₃COOH) δ 3.33 (s,3H), 3.45 (t,2H), 3.89(t,2H), 7.45-7.59 (m,3H), 7.79 (d,2H,J=7.04), 7.86-7.99 (m,2H),8.06-8.14 (m,3H), 8.26-8.31 (dd,1H, J=1.34, 8.4), 8.44-8.49(dd,1H,J=1.02,8.82), 8.72 (s,2H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ27.71, 58.30, 68.17, 111.7, 113.69, 114.57, 115.22, 115.72, 116.19,118.51, 123.94, 124.21, 125.26, 125.61, 127.46, 128.14, 129.36, 131.65,131.71, 132.91, 133.49, 137.24, 138.72, 139.68, 150.15, 153.24, 155.27;HRMS (FAB) calculated for C₃₀H₂₅N₆O (MH⁺) 485.2089 found 485.2089.

The intermediate 5-formyl-2-(2-methoxyethyl)benzimidazole was preparedas follows.

a. 5-Cyano-2(2-methoxyethyl)benzimidazole. 3,4-Diaminobenzonitrile (0.2g, 1.5 mmol) was refluxed with (0.22 ml, 2.25 mmol) of2-methoxypropionic acid in 4N HCl (2.5 ml) for 7 hours. Afterneutralization with 2N NaOH the mixture was extracted with ethyl acetateand dried over anhydrous Na₂SO₄ and concentrated in vacuo. The productwas purified on column chromatography using (7-100%) ethylacetate/n-hexanes to give a 50% yield of pure white product; mp 122-123°C.; IR (KBr) 2875, 2225, 1624, 1544, 1454, 1288, 1215, 1106, 824; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 3.29 (s,3H), 3.42 (t,2H), 3.84 (t,2H),7.87-8.00 (m,2H), 8.40 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ27.65, 58.18, 68.02, 106.79, 115.56, 118.28, 119.37, 128.95, 131.31,134.26, 156.12; Anal. calculated for C₁₁H₁₁N₃.½ H₂O: C; 62.84, H; 5.75,N; 19.97 found C; 62.71, H; 5.70, N; 18.83.

b. 5-Formyl-2-(2′-methoxyethyl)benzimidazole.5-Cyano-2-(2-methoxyethyl)benzimidazole (0.12 g, 0.61 mmol) was mixed inHCOOH (9 ml) and water (1 ml), to which was added Ni-Al (0.6 g). Themixture was heated at 95° C. for 5.5 hours. The mixture was passedthrough a celite bed while hot and the bed was washed with methanol andthe filtrate concentrated. After neutralization with 2N NaOH andextraction with CHCl₃, the extracts were dried over anhydrous Na₂SO₄ andconcentrated in vacuo. The residue was purified by column chromatographyusing a gradient of 15-100% ethyl acetateln-hexanes to give a whiteproduct in 65% yield; mp 83-84° C.; IR (Nujol) 2846, 2728, 1692, 1290,1109,816; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 3.31(s,3H), 3.44 (t,2H),3.86 (t,2H), 7.79-8.09 (m,2H), 8.36 (s,1H), 10.16 (s,1H); ¹³C NMR(DMSO-d₆+3 drops CF₃COOH) δ 27.73, 58.28, 68.08, 114.92, 116.86, 125.92,131.55, 133.85, 135.19, 155.8, 192.43; Anal. calculated for C₁₁H₁₂N₂O₂¼H₂O: C; 64.69, H; 5.92, N; 13.71 found C; 64.76, H; 6.02, N; 13.60.

Example 115-Bromo-2-[2′-[2″-hydroxybenzimidazol-5″-yl]benzimidazol-5′-yl]benzimidazole(18).

5-Bromo-2-[3,4-diaminophenyl]benzimidazole (33.3 mg, 0.11 mmol) and5-formyl-2-hydroxybenzimidazole (17.7 mg, 0.11 mmol) were heated at 145°C. in nitrobenzene (3 ml) overnight. Nitrobenzene was removed with aKugelrohr and the compound was purified by flash column chromatography.Elution with (5-15%) methanol/ethyl acetate gave 23.5 mg (0.05 mmol) ofyellow colored compound in 48% yield; mp>280° C.; IR (KBr) 3409, 3211,1698, 1558, 1482, 1384, 1279; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 7.30(d,1H,J=8.34), 7.69 (dd,1H, J=1.80, 8.71), 7.82 (s,1H), 7.86-7.99(m,2H), 8.09-8.13 (m,2H), 8.32 (dd,1H,J=1.36,8.69), 8.61 (s,1H), 11.38(s, 1H); ¹³C (DMSO-d₆+3 drops CF₃COOH) δ 108.01, 10.55, 113.92, 115.16,115.27, 116.25, 117.19, 117.86, 121.06, 122.41, 125.24, 128.70, 130.78,132.66, 133.16, 134.85, 134.89, 135.62, 150.42, 153.09, 155.69; HRMS(FAB) calculated for C₂₁H₁₄BrN₆O (MH⁺) 445.0412 found 445.0408.

The intermediate 5-bromo-2-[3,4-diaminophenyl]benzimidazole was preparedas follows.

a. 4-Bromo-o-phenylenediamine. 4-Bromo-2-nitroaniline 600 mg (2.76 mmol)was dissolved in 25 ml absolute ethanol and 2.72 g (14 mmol) SnCl₂ wasadded. The mixture was refluxed overnight. Ethanol was removed in vacuoand the mixture basified with 2N NaOH to pH 11. Ether extraction, dryingthe ether layer over anhydrous Na₂SO₄ and concentration in vacuoafforded 486 mg (2.6 mmol, 94% yield) of the crude4-bromo-o-phenylenediamine which was used for the next step withoutcharacterization.

b. 5-Bromo-2-[3,4-nitrophenyl]benzimidazole. 4-Bromo-o-phenylenediamine(275 mg, 1.5 mmol) and 3,4-dinitrobenzaldehyde (300 mg, 1.5 mmol) in 2ml nitrobenzene were heated at 145° C. overnight. The nitrobenzene wasremoved with a Kugelrohr. Column purification (1-10 % ethylacetate/n-hexanes) afforded 209 mg (0.57 mmol, 39% yield) of the pureproduct; ¹H NMR (DMSO+3 drops CF₃ COOH)δ 7.48 (dd,1H,J=1.82,8.76), 7.7(d,1H,8.76), 7.96 (d,1H, 1.46), 8.45 (d,1H,8.5), 8.68(dd,1H,J=1.84,8.5), 8.93 (d,1H,1.84); ¹³C NMR (DMSO+3 drops CF₃COOH) δ116.36, 117.48, 118.66, 123.74, 127.05, 132.07, 134.49, 137.59, 140.23,142.39, 142.81, 148.45.

c. 5-Bromo-2-[3,4-diaminophenyl]benzimidazole.5-Bromo-2-[3,4-dinitrophenyl]benzimidazole (140 mg, 0.38 mmol) wasdissolved in 8 ml absolute ethanol. 0.8 g SnCl₂ (4.2 mmol) was added andthe mixture refluxed overnight. Ethanol was removed in vacuo and themixture basified with 2N NaOH to pH 11. Repeated extraction with ether,drying the ether layer over anhydrous Na₂SO₄ and concentration in vacuoyielded (0.11 g, 0.37 mmol) of the crude diamine in 98% yield. Thediamine was used without further purification; ¹H NMR (DMSO-d₆) δ 6.63(d,1H,J=8.1), 7.26 (m,2H), 7.39 (m,2H), 6.65 (d,1H,J=1.76).

The intermediate 5-formyl-2-hydroxybenzimidazole was prepared asfollows.

d. 5-Cyano-2-hydroxybenzimidazole. 3,4-Diaminobenzonitrile (0.5 g, 3.8mmol) and urea (0.25 g, 4.2 mmol) were heated together in 1 ml DMF at145-150° C. for 9 h. The DMF was concentrated in vacuo and the mixturewas suspended in water and extracted with ethyl acetate. Purification bycolumn chromatography (elution with 60/40 ethyl acetate/n-hexanes)provided (0.53 g, 3.3 mmol) a yield of 89% of the product; IR (KBr)3533, 3209, 2224, 1732, 1482, 1281; ¹H NMR (DMSO-d₆+3 drops CF₃ COOH) δ7.1 (d,1H,J=8.06), 7.09-7.41 (m,2H), 11.06 (s,1H), 11.19 (s,1H); ¹³C NMR(DMSO-d₆+3 drops CF₃COOH) δ 102.52,109.36, 111.61, 120.04, 126.03,130.18, 133.93, 155.41.

e. 5-Formyl-2-hydroxybenzimidazole. 5-Cyano-2-hydroxybenzimidazole (0.5g, 3.14 mmol) was mixed with Ni-Al catalyst (3 g), HCOOH (45 ml) andwater (3 ml) and heated to reflux for 12 hrs. The hot mixture wasfiltered through a bed of celite and the filtrate concentrated in vacuo.pH of the mixture was adjusted to 9 with 2N NaOH and extraction wascarried out with ethyl acetate. The ethyl acetate layer was dried overanhydrous Na₂SO₄ and concentrated in vacua. Column chromatographicpurification, and elution with 65/35 ethyl acetate/n-hexanes provided0.4 g (2.4 mmol, 76% yield) of the final compound; IR (KBr) 3261, 3160,1677, 1631, 1477, 1282, 711; ¹H NMR (DMSO-d₆+3 drops CF₃ COOH) δ 7.11(d,1H,J=8.0), 7.41 (s,1H), 7.57 (dd,1H,J=1.54,8.0), 9.86 (s,1H), 10.99(s,1H), 11.17 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃ COOH) δ 108.15,108.67, 125.37, 130.1, 130.42, 135.64, 155.68, 191.99.

Example 125,6-Dibromo-2-[2′-(2″-trifluoromethylbenzimidazol-5″-yl)benzimidazol-5′yl]benzimidazole(22).

4,5-Dibromo-o-phenylenediamine (60 mg, 0.22 mmol) and5-formyl-2-(2′-trifluoromethylbenzimidazol-5′-yl)benzimidazole (73 mg,0.22 mmol) were heated in 10 ml nitrobenzene overnight at 150° C. Thenitrobenzene was removed witha Kugelrohr and the mixture loaded on acolumn. Elution with 90/10 ethyl acetate/n-hexanes yielded 25 mg (20%yield, 0.05 mmol) of compound; mp>260° C.; ¹H NMR (DMSO-d₆+3 dropsCF₃COOH) δ 8.02-8.09 (m,2H), 8.14 (s,2H), 8.26-8.29 (m,2H), 8.57 (s,1H),8.69 (s,1H).

The intermediate5-formyl-2-(2′-trifluoromethylbenzimidazol-5′-yl)benzimidazole wasprepared as follows.

a. 5-Cyano-2-(2′-trifluoromethylbenzimidazol-5′-yl)benzimidazole.5-formyl-2-trifluoromethylbenzimidazole (1.5 g, 7 mmol) was mixed with0.93 g of 3,4-diaminobenzonitrile (7 mmol) and 15 ml nitrobenzene. Themixture was heated overnight at 145° C. Nitrobenzene was removed with aKugelrohr and the mixture was loaded onto a column. Elution with 40/60ethyl acetate/n-hexanes gave 0.9 g (2.75 mmol) of the compound in 40%yield; mp>260° C.; IR (KBr) 3254, 2916, 2223, 1614, 1175; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 7.74 (dd,1H,J=1.38,8.4), 7.88 (d,1H,J=8.14),7.98 (d,1H,J=8.78), 8.25-8.03 (m,2H), 8.63 (s,1H); ¹³C NMR (DMSO-d₆ +3drops CF₃COOH) δ 105.62, 115.78, 116.35, 120.26, 123.06, 123.82, 127.18,137.35, 139.65, 142.17, 142.96, 154.13.

b. 5-Formyl-2-(2′-trifluoromethylbenzimidazol-5′-yl)benzimidazole.5-Cyano-2-(2′-trifluoromethylbenzimidlazol-5′-yl)benzimidazole (0.18 g,0.54 mmol) was refluxed in 8 ml HCOOH with 2.5 ml water and 0.6 g Ni-Alcatalyst for 7 hours at 110° C. The hot mixture was filtered throughcelite bed and the filtrate concentrated and its pH adjusted to 9.0 with2N NaOH. Repeated extraction with ethyl acetate, drying the organiclayer with anhydrous Na₂SO₄ and concentration in vacuo gave the crudeproduct. Purification by column chromatography (elution with 1%methanol/ethyl acetate) yielded 87 mg (0.26 mmol, 49% yield) of the purealdehyde; mp>260° C.; IR (KBr) 3411, 2966, 1679, 1310, 1153; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 7.96-8.06 (m,3H), 8.30-8.32 (m,2H), 8.57(s,1H), 10.15 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 106.77,112.51, 113.28, 117.79, 117.84, 118.28, 121.78, 123.96, 125.02, 132.98,135.79, 139.62, 142.48, 153.51, 192.65.

The intermediate 4,5-dibromo-1,2-phenylenediamine was prepared asfollows, using a modification of the procedures described in U.S. Pat.No. 4,264,600.

c. 3,4-Dibromoaniline. 3-Bromoaniline (3 g, 17.4 mmol) was dissolved in15 ml CH₂Cl₂ and the reaction mixture was cooled to −10° C. in anice-salt bath. 2,4,4,6-Tetrabromo-2,5-cyclohexadienone, (9.29 g, 0.02mmol) was added in small portions with constant stirring. The reactionmixture was stirred for a period of 7 hours at 0° C. after which thereaction was quenched with 2N NaOH (10 ml). The aqueous layer wasextracted with CH₂Cl₂ and the organic layer was dried over anhydrousNa₂SO₄. The CH₂Cl₂ layer was concentrated in vacuo and purified bycolumn chromatography. Elution with 0-3% ethyl acetate/n-hexanes yielded3.2 g (12.7 mmol, 73%) of pure product; mp 80-81° C.; IR (KBr) 3406,3318, 3210, 1583, 1464, 1287, 1108, 860, 668; ¹H NMR (CDCl₃) δ 6.49(dd,1H,J=2.7,8.6), 6.7 (d,1H,J=2.64), 7.32 (d,1H,J=8.6); ¹³C NMR(CDCl₃)δ 112.6, 116, 120.1, 125.45, 134.26, 147.08.

d. 3,4-Dibromoacetanilide. 3,4-Dibromoaniline (3.2 g, 12.7 mmol) wasmixed with 13 ml acetic anhydride and heated at 110° C. for 2 hoursafter which it was poured over ice cold water. The aqueous layer wasextracted with ethyl acetate, 0.1N HCl and 1N NaOH, and the organiclayer was dried over anhydrous Na₂SO₄. The organic layer wasconcentrated in vacuo and purified by column chromatography. Elutionwith 1-50% ethyl acetate/n-hexanes yielded 2.6 g (9 mmol, 71% yield) ofthe acetanilide: mp 91-93° C.; IR (KBr) 3293, 3172, 1668, 1589,1552,1522, 1373, 813; ¹H NMR (CDCl₃) δ 2.17(s,3H), 7.33 (dd,1H,J=2.4,8.66),7.52 (d,1H,J=8.68), 7.87 (d,1H, J=2.4); ¹³C NMR (CDCl₃) δ 25.07, 119.64,120.35, 125.04, 125.38, 134.13, 138.40, 168.96.

e. 3,4-Dibromo-6-nitroacetanilide. 3,4-Dibromoacetanilide (2.64 g, 9mmol) was dissolved in 8 ml conc. H₂SO₄ (chilled in ice-salt bath) at atemperature of 0° C. To this solution was added 1 ml chilled nitratingmixture (equal volumes of conc. H₂SO₄ and fuming HNO₃) and the mixturestirred for 20 min. The reaction mixture was poured into ice water andneutralized with ammonium hydroxide to pH of 9.0. The yellow precipitatewas filtered and purified by column chromatography. Elution with 1-4%ethyl acetate/n-hexanes yielded 2.1 g (6.15 mmol, 68%) of the3,4-dibromo-6-nitroacetanilide: mp 141-142° C.; IR (KBr) 3340, 3128,1693, 1569, 1479, 1332, 1268; ¹H NMR (CDCl₃) δ 2.3 (s,3H), 8.46 (s, 1H),9.22 (s,1 H); ¹³C NMR (CDCl₃) δ 26.14, 118.67, 126.86, 130.86, 134.51,134.59, 136.98, 169.40.

f. 3,4-Dibromo-6-nitroaniline. 3,4-Dibromo-6-nitroacetanilide (2.1 g,6.15 mmol) was heated to refluxing temperature for 2 hours with 40 ml of6N HCI. The reaction mixture was then poured over an ice-water mixtureand stirred. The pH of the solution was adjusted to 9.0 with NaOH. Theresulting bright yellow precipitate was filtered, washed with cold waterand dried to yield (1.78 g, 6 mmol, 98%) of pure product; mp 204-205°C.; IR (KBr) 3475, 3355, 3097, 1612, 1478, 1241, 1122, 914; ¹H NMR(CDCl₃) δ 6.05 (brs,2H), 7.18 (s,1H), 8.37 (s,1H); ¹³C NMR (CDCl₃) δ111.23, 123.22, 129.34, 130.59, 133.61, 142.36.

g. 4,5-Dibromo-1,2-phenylenediamine. 3,4-Dibromo-6-nitroaniline (189 mg,0.64 mmol) was dissolved in 8 ml anhydrous ethanol to which was addedabout 400 mg Raney Nickel. The hydrogenation apparatus was at a hydrogenpressure 50 psi. After 45 min. the deep yellow color originally presentwas completely discharged indicating complete reduction of the nitro tothe amine groups. The reaction mixture was filtered through celite andthe bed was washed with methanol. The methanol was concentrated in vacuoto give 135 mg of the crude diamine in 82% yield. The crude diamine wasused as such without further purification; ¹H NMR (CDCl₃) δ 3.37(br,4H), 6.93 (s,2H); ¹³CNMR (CDCl₃) δ 113.98, 120.95, 135.84.

Example 135-Phenyl-6methoxy-2-[2′(benzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(15).

4-Methoxy-5-phenyl-1,2 phenylenediamine (139 mg, 0.65 mmol) and5-formyl-2-(benzimidazol-5′-yl)benzimidazole (170 mg, 0.65 mmol) wereheated together in nitrobenzene (5 ml) overnight at 145° C. Nitrobenzenewas removed with a Kugelrohr and the compound was loaded onto a column.(1-10%) methanol/ethyl acetate gave 120 mg (41%) of pure product;mp>280° C.; IR (KBr) 3298, 3050, 2987, 1630, 1541, 1438, 1283; ¹H NMR(DMSO-d₆+3 drops CF₃COOH) δ 3.92 (s,3H), 7.39-7.57 (m,6H), 7.72 (s,1H),8.11-8.15 (m,1H), 8.19-8.27 (m,2H), 8.47 (dd,1H,J=1.46,8.07), 8.64(s,1H), 8.76 (s,1H), 9.75 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ56.40, 95.73, 114.62, 115.18, 116.02, 116.15, 119.03, 119.07, 125.59,126.29, 127.63, 127.67, 128.34, 129.79, 130.69, 131.54, 132.42, 133.38,137.59, 148.81, 152.84, 156.82; HRMS (FAB) calculated for C₂₈H₂₁N₆O(MH⁺) 457.1777, found 457.1770.

The intermediate 4-methoxy-5-phenyl-1,2 phenylenediamine was prepared asfollows.

a. 4-Methoxy-2-nitro5-phenylaniline. 3-Bromo4-methoxy-6-nitroaniline(400 mg, 1.62 mmol) was dissolved in DME (20 ml). Tetrakispalladiumtriphenyl phosphine (94 mg, 0.08 mmol) served as the catalyst. To thismixture was added phenyl boronic acid(300 mg, 1.01 mmol) and 2M Na₂CO₃(1.8 ml) and the mixture refluxed at 90° C. overnight. The reactionmixture was concentrated in vacuo and purified by flash columnchromatography. (1-10%) ethyl acetate/n-hexanes gave 280 mg (1.14 mmol)of pure product in 71% yield; IR (KBr) 3435, 3328, 2933, 1570, 1480,1227, 1029, 692; ¹H NMR (CDCl₃) δ 3.80 (s,3H), 5.94 (br,2H), 6.79(s,1H), 7.39-7.64 (m,5H), 7.64 (s,1H); ¹³C NMR (CDCl₃) δ 56.63, 106.76,121.26, 128.69, 128.72, 128.76, 128.79, 128.92, 129.71, 136.69, 140.24,141.42, 148.65; MS (FAB) calculated for C₁₃H₁₂N₂O₃ 244.0848, found244.0847.

b. 4-Methoxy-5-phenyl-1,2 phenylenediamine.4-Methoxy-2-nitro-5-phenyl-aniline (165 mg, 0.68 mmol) in ethyl acetate(20 ml) was reduced using 20 mg of 10% Pd/C as the catalyst, overnight.The mixture was filtered through celite bed and the bed was washed withmethanol. All the washings were concentrated in vacuo to yield 139 mg(96% yield) of the crude diamine which was used without furtherpurification; ¹H NMR (CDCl₃) δ 3.49 (brs,4H), 3.71 (s,3H), 6.42 (s, 1H),6.74 (s,1H), 7.26-7.52 (m,5H); ¹³C NMR (CDCl₃) δ 56.81, 101.77, 120.93,127.53, 128.39, 128.45, 128.49, 129.82, 129.96, 136.64, 139.17, 142.37,153.73.

The intermediate 3-bromo-4-methoxy-6-nitro-aniline used in sub-part a iscommercially available (Aldrich Chemical Company).

The intermediate 5-fornyl-2-(benzimidazol-5′-yl)benzimidazole wasprepared as described by Sun et al. J. Med. Chem. 1995, 38, 3638-3644.

Example 145,6-Diphenyl-2-[2′(benzimidazol-5″-yl)benzimidazol-5′-yl]benzimidazole(16).

4,5-Diphenyl-1,2-phenylenediamine (151 mg, 0.58 mmol) and5-formyl-2-(benzimidazol-5′-yl)benzimidazole (152 mg, 0.58 mmol) wereheated in nitrobenzene (4 ml) overnight at 145° C. under nitrogen. Thenitrobenzene was removed with a Kugelrohr. Compound was purified byflash column chromatography. Elution with (2-10%) methanol/ethyl acetategave 108 mg (0.22 mmol) of pure yellow compound in 37% yield. mp>280°C.; IR (KBr) 3399, 3059, 1629, 1551, 1441, 1292; ¹H NMR (DMSO-d₆ +3drops CF₃COOH) δ 7.17-7.33 (m,10H), 7.84 (s,2H),8.06-8.25 (m,3H), 8.49(dd,1H,J=1.18,8.89), 8.66 (s,1H), 8.75 (s,1H), 9.69 (s,1H); ¹³C NMR(DMSO-d₆+3 drops CF₃COOH) δ 113.94, 115.24, 115.84, 116.15, 116.32,117.89, 123.34, 126.32, 126.66, 127.86, 128.38, 128.42, 128.46, 130.05,131.77, 131.89, 133.03, 138.87, 138.97, 140.62, 141.19, 160.97, 153.71;HRMS (FAB) calculated for C₃₃H₂₃N₆ (MH⁺) 503.1984 found 503.1989.

The intermediate 4,5-diphenyl-1,2-phenylenediamine was prepared asfollows.

a. 4,5-Diphenyl-2-nitroaniline. 3,4-Dibromo-6-nitroaniline (332 mg, 1.12mmol) was dissolved in DME (20 ml).Tetrakis(triphenylphosphine)palladium (65 mg, 0.06 mmol), phenyl boronicacid (200 mg, 1.64 mmol), and 2M Na₂CO₃ (10 ml) were added to thereaction mixture and refluxed at 90° C. overnight. The reaction mixturewas concentrated in vacuo and loaded onto a column. (1-3%) ethylacetate/n-hexanes afforded 259 mg of pure yellow compound in 80% yield;mp 139-141° C.; IR (KBr) 3476, 3363, 2924, 1621, 1476, 1263, 1089; ¹HNMR (CDCl₃) δ 6.11 (brs,2H), 6.86 (s,1H), 7.04-7.09 (m,5H), 7.15-7.26(m,5H), 8.21 (s,1H); ¹³C NMR (CDCl₃) δ 120.56, 127.22, 127.66, 128.20,128.26, 128.52, 128.53, 129.31, 129.39, 129.47, 129.77, 130.14, 130.93,131.79, 139.85, 139.94, 144.08, 149.03.

b. 4,5-Diphenyl-1,2-phenylenediamine. 4,5-Diphenyl-2-nitroaniline (200mg, 0.69 mmol) in ethanol (50 ml) was reduced using 40 mg 10% Pd/C.Hydrogenation was carried out at 40 psi pressure for 10 hours. Themixture was filtered through celite and the bed washed with methanol.The methanol layer was concentrated in vacuo to yield 151 mg of thecrude diamine in 84% yield. The crude diamine was used as such withoutpurification. ¹H NMR (CD₃OD) δ 6.78 (s,2H), 7.01-7.16 (m,10H); ¹³C NMR(CD₃OD) δ 118.08, 121.23, 127.17, 127.66, 130.44, 131.76, 138.32.

Example 15 5,6-Dibromo-2-[2′-(benzimidazol-5″-yl)benzimidazol-5′yl]benzimidazole (20).

4,5-Dibromo-1,2-phenylenediamine (128 mg, 0.48 mmol) and5-formyl-2-(benzimidazol-5′-yl)benzimidazole (126 mg, 0.48 mmol) wereheated in nitrobenzene (6 ml) at 145° C. overnight. The nitrobenzene wasremoved with a Kugelrohr and the mixture loaded on a column forpurification. Elution with (1-10%) methanol/ethyl acetate gave 0.1 gm(41%) of pure compouind; mp>260° C.; IR(KBr) 3405, 3198, 1626, 1544,1385, 1292; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 8.03-8.13 (m,2H), 8.17(s,2H), 8.25 (d,1H,J=9.16), 8.42 (d,1H,J=8.64), 8.59 (s,1H), 8.74(s,1H), 9.75 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 114.73, 114.96,115.77, 115.99, 118.93, 119.61, 120.73, 123.29, 124.47, 125.56, 131.49,133.47, 134.77, 135.79, 137.95, 151.93, 152.31; HRMS (FAB) calculatedfor C₂₁H₁₃Br₂N₆ (MH⁺) 506.9568 found 506.9574.

The intermediate 4,5-dibromo-1,2-phenylenediamine was prepared asdescribed at Example 12c-g.

Example 165-Bromo-6-metboxy-2-[2′-(benzimidazol-5″-yl)benzimidazol-5′yl]benzimidazole(21)

In nitrobenzene (4ml), 4-bromo-5-methoxy-1,2-phenylenediamine (123 mg,0.57 mmol) and 5-formyl-2-(benzimidazol-5′-yl)benzimidazole (150 mg,0.57 mmol) were heated at 145° C. overnight under nitrogen. Nitrobenzenewas removed with a Kugelrohr. Chromatographic separation with (1-10%)methanol/ethyl acetate afforded 104 mg (40%) of pure compound; mp >280°C.; ¹H NMR (DMSO-d₆+3 drops CF₃COOH) δ 3.91 (s,3H), 7.17-7.29 (m,1H),7.78 (d,1H,J=8.84), 8.00-8.13 (m,3H), 8.49-8.53 (m,1H), 8.66 (s,1H),8.79 (s,1H), 9.69 (s,1H); ¹³C NMR (DMSO-d₆+3 drops CF₃COOH) δ 56.16,96.43, 114.06, 114.97, 115.55, 115.79, 115.89, 116.35, 117.97, 118.42,123.11, 125.30, 125.58, 126.33, 127.43, 131.85, 133.05, 133.11, 138.39,140.84, 149.04, 153.44; HRMS (FAB) calculated for C₂₂H₁₆BrN₆O (MH⁺)

The intermediate 4-bromo-5-methoxy-1,2-phenylenediamine was prepared asfollows.

a. 4-Bromo-5-methoxy-1,2-phenylenediamine.3-Bromo-4-methoxy-6-nitroaniline (150 mg, 0.61 mmol) (Aldrich ChemicalCompany) was dissolved in ethanol (10 ml) and hydrogenation was carriedout using 350 mg Raney Nickel for 30 min. The reaction mixture wasfiltered through celite bed and washed with methanol. The methanoliclayer was dried in vacuo to give 127 mg of the crude diamnine in 97.40%yield, which was used as such withoult purification; ¹H NMR (CDCl₃) δ3.20 (brs,2H), 3.39 (brs,2H), 3.8 (s,3H), 8.36 (s,1H), 6.89 (s,1H); ¹³CNMR (CDCl₃) δ 57.35, 100.38, 102.27, 122.52, 128.69, 136.68, 150.94.

Example 17

The following illustrate representative pharmaceutical dosage forms,containing a compound of formula I (‘Compound X’), for therapeutic orprophylactic use in humans.

(i) Tablet 1 mg/tablet ‘Compound X’ 100.0 Lactose 77.5 Povidone 15.0Croscarmellose sodium 12.0 Microcrystalline cellulose 92.5 Magnesiumstearate 3.0 300.0 (ii) Tablet 2 mg/tablet ‘Compound X’ 20.0Microcrystalline cellulose 410.0 Starch 50.0 Sodium starch glycolate15.0 Magnesium stearate 5.0 500.0 (iii) Capsule mg/capsule ‘Compound X’10.0 Colloidal silicon dioxide 1.5 Lactose 465.5 Pregelatinized starch120.0 Magnesium stearate 3.0 600.0 (iv) Injection 1 (1 mg/ml) mg/ml‘Compound X’ (free acid form) 1.0 Dibasic sodium phosphate 12.0Monobasic sodium phosphate 0.7 Sodium chloride 4.5 1.0N Sodium hydroxidesolution q.s. (pH adjustment to 7.0-7.5) Water for injection q.s. ad 1mL (v) Injection 2 (10 mg/ml) mg/ml ‘Compound X’ (free acid form) 10.0Monobasic sodium phosphate 0.3 Dibasic sodium phosphate 1.1 Polyethyleneglycol 400 200.0 01N Sodium hydroxide solution q.s. (pH adjustment to7.0-7.5) Water for injection q.s. ad 1 mL (vi) Aerosol mg/can ‘CompoundX’ 20.0 Oleic acid 10.0 Trichloromonofluoromethane 5,000.0Dichlorodifluoromethane 10,000.0 Dichlorotetrafluoroethane 5,000.0

The above formulations may be obtained by conventional procedures wellknown in the pharmaceutical art.

All publications, patents, and patent documents are incorporated byreference herein, as though individually incorporated by reference. Theinvention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention.

What is claimed is:
 1. A compound of formula I:

wherein R₁ and R₂ are each independently hydrogen, (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio,(C₁-C₆)alkanoyloxy, aryl, heteroaryl, aryl(C₁-C₆)alkyl, orheteroaryl(C₁-C₆)alkyl; or R₁ and R₂ taken together are methylenedioxy;or R₁ and R₂ taken together are benzo; R₃, R₄, and R₅ are eachindependently selected from the group consisting of hydrogen,(C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₂-C₆)alkanoyloxy, aryl, heteroaryl, aryl(C₁-C₆)alkyl, andheteroaryl(C₁-C₆)alkyl; R₆ and R₇ are each independently hydrogen,(C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl,(C₁-C₆)alkoxy, (C₃-C₆)ycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro,cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy; R₈ is hydroxy, halo, nitro,cyano, mercapto, carboxy, (C₁-C₆)alkoxy, (C₃-C₆)cycloalkyl(C₁-C₆)alkoxy,—NR_(a)R_(b), halo(C₁-C₆)alkyl, trifluoromethoxy, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, (C₁-C₆)alkanoyloxy, aryloxy, orheteroaryloxy; or R₈ is (C₁-C₆)alkyl substituted by 1, 2, or 3substituents independently selected from the group consisting ofhydroxy, nitro, cyano, mercapto, carboxy, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, —NR_(a)R_(b), trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio,(C₁-C₆)alkanoyloxy, aryloxy, and heteroaryloxy; and each R_(a) and R_(b)is independently hydrogen, (C₁-C₆)alkyl, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, aryl, heteroaryl, aryl(C₁-C₆)alkyl,heteroaryl(C₁-C₆)alkyl, arylcarbonyl, or heteroarylcarbonyl; or R_(a)and R_(b) together with the nitrogen to which they are attached arepyrrolidino, piperidino, or morpholino. wherein any aryl, heteroaryl, orbenzo of R₁-R₅, R₈, R_(a), and R_(b) may optionally be substituted by 1,2, or 3 substituents independently selected from the group consisting of(C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl,(C₁-C₆)alkoxy, (C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro,cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, and (C₁-C₆)alkanoyloxy; or a pharmaceuticallyacceptable salt thereof.
 2. The compound of claim 1 wherein R₂ isphenyl, optionally substituted by 1, 2, or 3 substituents independentlyselected from the group consisting of (C₁-C₆)alkyl, (C₁-C₆)alkoxy,hydroxy, halo, nitro, cyano, mercapto, carboxy, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, and (C₁-C₆)alkanoyloxy.
 3. The compound of claim 1wherein R₂ is phenyl.
 4. The compound of claim 1 wherein R₁ is hydrogen.5. The compound of claim 1 wherein R₁ is halo.
 6. The compound of claim1 wherein R₁ and R₂ are each halo.
 7. The compound of claim 1 wherein R₁and R₂ are each bromo.
 8. The compound of claim 1 wherein R₃, R₄, and R₅are each hydrogen.
 9. The compound of claim 1 wherein R₆ and R₇ are eachhydrogen.
 10. The compound of claim 1 wherein R₆ is (C₁-C₆)alkoxy,hydroxy, halo, nitro, cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl,halo(C₁-C₆)alkyl, trifluoromethoxy, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 11. Thecompound of claim 1 wherein R₇ is (C₁-C₆)alkoxy, hydroxy, halo, nitro,cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 12. The compound of claim 1wherein R₈ is hydroxy, halo, nitro, cyano, mercapto, carboxy,(C₁-C₆)alkoxy, —NR_(a)R_(b), halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or(C₁-C₆)alkanoyloxy.
 13. The compound of claim 1 wherein R₈ is(C₁-C₆)alkyl substituted by 1, 2, or 3 hydroxy, nitro, cyano, mercapto,carboxy, (C₁-C₆)alkoxy, —NR_(a)R_(b), trifluoromethoxy, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 14. Thecompound of claim 1 wherein R₈ is (C₁-C₆)alkyl substituted by hydroxy,nitro, cyano, mercapto, carboxy, (C₁-C₆)alkoxy, —NR_(a)R_(b),trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 15. The compound of claim 1wherein R₈ is halo or trifluoromethyl.
 16. The compound of claim 1wherein R₈ is trifluoromethyl.
 17. A pharmaceutical compositioncomprising a compound of claim 1, in combination with a pharmaceuticallyacceptable carrier.
 18. A compound of formula I:

wherein R₁ and R₂ are each independently (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio,(C₁-C₆)alkanoyloxy, aryl, heteroaryl, aryl(C₁-C₆)alkyl, orheteroaryl(C₁-C₆)alkyl; or R₁ and R₂ taken together are methylenedioxy;R₃, R₄, and R₈ are each independently selected from the group consistingof hydrogen, (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₂-C₆)alkanoyloxy, aryl, heteroaryl,aryl(C₁-C₆)alkyl, and heteroaryl(C₁-C₆)alkyl; R₆ and R₇ are eachindependently hydrogen, (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or(C₁-₆)alkanoyloxy; and R₈ is hydrogen, (C₁-C₆)alkyl, aryl, orheteroaryl; wherein any aryl or heteroaryl of R₁-R₅ and R₈ mayoptionally be substituted by 1, 2, or 3 substituents independentlyselected from the group consisting of (C₁-C₆)alkyl, (C₃-C₆)cycloalkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and(C₁-C₆)alkanoyloxy; or a pharmaceutically acceptable salt thereof. 19.The compound of claim 18 wherein R₁ and R₂ are each independently(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto, carboxy,hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy, or aryl. 20.The compound of claim 18 wherein R₁ and R₂ taken together aremethylenedioxy.
 21. The compound of claim 18 wherein R₁ and R₂ are eachhalo.
 22. The compound of claim 18 wherein R₁ and R₂ are each bromo. 23.The compound of claim 18 wherein R₁ and R₂ are each independently phenylor methoxy.
 24. The compound of claim 18 wherein R₃, R₄, and R₅ are eachhydrogen.
 25. The compound of claim 18 wherein R₆ is (C₁-C₆)alkoxy,hydroxy, halo, nitro, cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl,halo(C₁-C₆)alkyl, trifluoromethoxy, (C₁-C₆)alkanoyl,(C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 26. Thecompound of claim 18 wherein R₇ is (C₁-C₆)alkoxy, hydroxy, halo, nitro,cyano, mercapto, carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl,trifluoromethoxy, (C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl,(C₁-C₆)alkylthio, or (C₁-C₆)alkanoyloxy.
 27. The compound of claim 18wherein R₈ is hydrogen.
 28. The compound of claim 18 wherein R₈ is(C₁-C₆)alkyl.
 29. The compound of claim 18 wherein R₈is aryl, optionallysubstituted by 1, 2, or 3 substituents independently selected from thegroup consisting of (C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and(C₁-C₆)alkanoyloxy.
 30. The compound of claim 18 wherein R₈ isheteroaryl, optionally substituted by 1, 2, or 3 substituentsindependently selected from the group consisting of (C₁-C₆)alkyl,(C₃-C₆)cycloalkyl, (C₃-C₆)cycloalkyl(C₁-C₆)alkyl, (C₁-C₆)alkoxy,(C₃-C₆)cycloalkyl(C₁-C₆)alkoxy, hydroxy, halo, nitro, cyano, mercapto,carboxy, hydroxy(C₁-C₆)alkyl, halo(C₁-C₆)alkyl, trifluoromethoxy,(C₁-C₆)alkanoyl, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylthio, and(C₁-C₆)alkanoyloxy.
 31. A pharmaceutical composition comprising acompound of claim 18, in combination with a pharmaceutically acceptablecarrier.